Protein crystals are associated with progressive pulmonary fibrosis in conditional Nedd4-2 deficient mice

Recent studies have identified spontaneous protein crystallization as an enhancer of type 2 inflammation in eosinophilic airway diseases, but its function in other pulmonary pathologies has remained elusive. In this study, we investigated the role of spontaneous protein crystallization in conditional Nedd4-2 -/- mice, an established model for intersitial lung disease with progressive pulmonary fibrosis. Therefore, we analyzed lung morphology by histology, immunohistochemistry, and electron microscopy. Further, protein crystals were quantified in bronchoalveolar lavage (BAL) and correlated with inflammatory cell counts in BAL and pulmonary compliance. Finally, microarray analyzes were performed to investigate differentially expressed genes in conditional Nedd4-2 -/- mice. Chil3- and Chil4-positive protein crystals were observed in distal airways, localized both within alveolar macrophages and in terminal airways embedded in mucus plugs in conditional Nedd4-2 -/- mice. Crystal burden in BAL correlated with the severity of pulmonary inflammation and decline in lung compliance. Microarray analyzes demonstrated transcriptomic changes reflecting type 2 inflammation and extracellular matrix remodeling in conditional Nedd4-2 -/- mice. Our findings indicate that conditional Nedd4-2 deletion in mice leads to spontaneous Chil3 and Chil4 crystallization, type 2 inflammation, and progressive fibrotic tissue remodeling. These data provide a new mechanistic perspective in the development of chronic lung disease which may lead to the development of new therapies. Publication History Article published online: 26 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany